Catalyst components comprising a titanium compound and an electron donor compound supported on an active magnesium halide carrier are well known in the art. A usual active magnesium halide carrier is an adduct of a magnesium halide and an alcohol, generally in the form of spheric particles. Spheric catalysts are obtained by reacting the magnesium halide-alcohol adduct carrier with a titanium compound, such as a titanium halide, and an electron donor compound. When used in olefin polymerization, in particular in propylene polymerization, such catalysts exhibit high polymerization activities and high stereospecificities, and the resulting polymers have good particle morphology.
The disclosed magnesium halide-alcohol adduct carriers comprise generally only magnesium dichloride and an alcohol. Some of the disclosed magnesium halide-alcohol adduct carriers further comprise a minor amount of water. Such magnesium halide-alcohol adduct carriers may be prepared by known processes, such as spray drying process, spray cooling process, high-pressure extruding process, or high speed stirring process. See, for example, U.S. Pat. No. 4,421,674, U.S. Pat. No. 4,469,648, WO 08707620, WO 9311166, U.S. Pat. No. 5,100,849, U.S. Pat. No. 6,020,279, U.S. Pat. No. 4,399,054, EP0395083, U.S. Pat. No. 6,127,304, and U.S. Pat. No. 6,323,152.
Besides the above-mentioned magnesium halide-alcohol binary adduct carriers, the prior art also discloses other forms of active magnesium halide carriers. For example, CN1922212A discloses a carrier obtained by reacting a solution of a magnesium halide in a cyclic ether and an alcohol with a titanium halide. CN101190953A discloses a magnesium-containing adduct carrier formed by reacting a C1-C5 alcohol with powdery magnesium in the presence of a methyl halide. CN1590415A discloses a complex carrier prepared by reacting a C2-C4 lower alcohol with powdery magnesium in the presence of a methyl halide to form a homogeneous magnesium compound solution and supporting the formed magnesium compound on a spheric silica carrier. CN1016422B, U.S. Pat. No. 5,034,361, U.S. Pat. No. 5,849,655, U.S. Pat. No. 5,817,591 and U.S. Pat. No. 4,469,648 disclose active magnesium dichloride carriers prepared by using an alkoxy magnesium as a starting material.